Embodiments of the invention relate to a method for manufacturing an image sensor.
Image sensors are semiconductor devices that convert optical images to electrical signals, and of these, charge coupled devices (CCDs) have individual metal oxide silicon (MOS) capacitors that are tightly packed together, in which charge carriers are stored and transferred.
Complementary MOS (CMOS) image sensors are devices that use a switching method and that employ CMOS technology using control circuits and signal processing circuits as peripheral circuits and that detect outputs in sequence using a number of MOS transistors related to the number of pixels.
One obstacle that needs to be overcome in the manufacturing of image sensors is the conversion rate of incident light signals to electrical signals. In other words, sensitivity needs to be increased.
A microlens is formed on the uppermost layer of a CMOS image sensor. Light focused by the microlens is transmitted through a planarization layer and a color filter array layer, and is converted to electrical signals in a light collector such as a photodiode.
An image sensor uses signals that have been converted to electrical signals through the above process to display images. Here, the image is affected by factors such as the focal length of the microlens, the size and distribution of the color filter, the thickness of the planarization layer, and the pitch size of the photodiode.
Also, for forming microlenses that focus light, there have been many methods proposed for minimizing the gaps between neighboring microlenses or producing a zero gap therebetween.